Canister assemblies or more generally suction canisters are used as part of a vacuum assembly for the removal of liquids and gases that collect in body cavities because of disease, injury, or surgery. Suctioning may be used to clear passageways, such as tracheal or nasal gastric passageways or may be used in surgical procedures to remove blood and irrigating fluids.
Generally, the assembly includes a vacuum line leading from a motor pump or hospital wall central vacuum system assembly past a valve and gauge for controlling fluid flow therethrough. The line leads to a canister which is a collection mechanism for retaining fluids as a trap to prevent the fluids from being drawn into the motor pump. Patient tubing leads from the canister and may have a suction catheter tip mounted thereon.
The aspirated body fluids may contain infectious viruses and bacteria. If these aerosols or particulates are not trapped within the collection assembly, they can be drawn through the motor pump and into the surrounding environment of the patient and professionals or into the main hospital wall system which can cause contamination, corrosion, and gradual occlusion. Further, aspriation of aerosols through the fluid line and into the motor pump assembly can cause contamination and corrosion of the motor pump.
It is also necessary to prevent overflow of fluid retained in the canister from being drawn up into the suction line and into the motor pump walls. Various mechanisms have been used to prevent this occurrence. For example, a float member may be slidably mounted beneath the vacuum port leading to the motor pump. The float is constructed so that as the fluid volume within the canister rises, the float member perfects a seal against the vacuum port. These mechanisms present several problems. The moving mechanical valve generally is mounted on a post or a group of bosses upon which it slides. The post or bosses may become contaminated so as to cause sticking of the float member. Foaming is another problem which occurs within the canister. Foam rises quickly and may not raise the float while still being aspirated into the fluid line. Such premature shut-off can cause burning out of the vacuum pump motor and more critically, result in ineffective aspiration of a surgical site. At the other extreme, these mechanisms have been caused to prematurely seal the vacuum port by vibration or jarring.
Recently, manufacturers have disposed a filter element within the vacuum port in an attempt to trap the particulate matter escaping therethrough. These filters are retained in a housing wherein there is direct flow of fluid or air into the housing. The housing does not prevent splashing of fluid or foam against the filter. Further, a problem results from impaction of particles against the filter and from the passage of aerosol therethrough. The particles in these prior art systems are drawn forcefully into the canister and against the filter. Impaction of particles and aerosol on the filter decreases flow therethrough.
Other alternative constructions have included crude seals disposed over the vacuum port. An outer plug material having a spiral path extending therethrough and a central plug member disposed within the central portion thereof are used as a filtering device. Such a device is manufactured by Respiratory Care, Inc. of Chicago, Ill.
Various prior art assemblies including filtering mechanisms include filter supports providing a tortuous path for air and aerosols to be drawn through. For example, the U.S. Pat. No. 1,556,592 to Donaldson, issued Oct. 13, 1925 discloses an air cleaner including a filter wherein smoke filled air is drawn into the assembly through a tortuous path. The U.S. Pat. No. 1,735,441 to Paffen et al, issued Nov. 12, 1929 discloses an air compressor assembly wherein air is drawn through a tubing and against a deflector to remove oil droplets from the air prior to being drawing through a filter.
None of the aforementioned prior art assemblies provide means for effectively removing aerosols and particulates from fluid being drawn into a canister or for perfecting an effective seal against overflow of fluid or foam within the container. Aerosol entering into a canister from a lid member has an inertia as it is drawn into the canister. The particles will generally bounce off the sides and bottom of the canister and be deflected towards the vacuum or outlet port also located on the lid of the canister. Prior art filter mechanisms provide no means for effectively removing the aerosols and particulates, and at the same time preventing impaction of these materials directly against the filter material which can cause premature clogging of the filter.